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<title>XSAVE—Save Processor Extended States </title></head>
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<h1>XSAVE—Save Processor Extended States</h1>
<table>
<tr>
<th>Opcode</th>
<th>Instruction</th>
<th>Op/En</th>
<th>64-Bit Mode</th>
<th>Compat/Leg Mode</th>
<th>Description</th></tr>
<tr>
<td>0F AE /4</td>
<td>XSAVE <em>mem</em></td>
<td>M</td>
<td>Valid</td>
<td>Valid</td>
<td>Save state components specified by EDX:EAX to <em>mem</em>.</td></tr>
<tr>
<td>REX.W+ 0F AE /4</td>
<td>XSAVE64 <em>mem</em></td>
<td>M</td>
<td>Valid</td>
<td>N.E.</td>
<td>Save state components specified by EDX:EAX to <em>mem</em>.</td></tr></table>
<h3>Instruction Operand Encoding</h3>
<table>
<tr>
<td>Op/En</td>
<td>Operand 1</td>
<td>Operand 2</td>
<td>Operand 3</td>
<td>Operand 4</td></tr>
<tr>
<td>M</td>
<td>ModRM:r/m (w)</td>
<td>NA</td>
<td>NA</td>
<td>NA</td></tr></table>
<h2>Description</h2>
<p>Performs a full or partial save of processor state components to the XSAVE area located at the memory address specified by the destination operand. The implicit EDX:EAX register pair specifies a 64-bit instruction mask. The specific state components saved correspond to the bits set in the requested-feature bitmap (RFBM), which is the logical-AND of EDX:EAX and XCR0.</p>
<p>The format of the XSAVE area is detailed in Section 13.4, “XSAVE Area,” of <em>Intel® 64 and IA-32 Architectures Soft-ware Developer’s Manual, Volume 1</em>.</p>
<p>Section 13.7, “Operation of XSAVE,” of <em>Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1 </em>provides a detailed description of the operation of the XSAVE instruction. The following items provide a high-level outline:</p>
<p>Use of a destination operand not aligned to 64-byte boundary (in either 64-bit or 32-bit modes) results in a general-protection (#GP) exception. In 64-bit mode, the upper 32 bits of RDX and RAX are ignored.</p>
<h2>Operation</h2>
<pre>RFBM ← XCR0 AND EDX:EAX;
                                    /* bitwise logical AND */
OLD_BV ← XSTATE_BV field from XSAVE header;
IF RFBM[0] = 1
    THEN store x87 state into legacy region of XSAVE area;
FI;
IF RFBM[1] = 1
    THEN store XMM registers into legacy region of XSAVE area;
FI;
1.
    An exception is made for MXCSR and MXCSR_MASK, which belong to state component 1 — SSE. XSAVE saves these values to mem-ory if either RFBM[1] or RFBM[2] is 1.
IF RFBM[2] = 1
    THEN store AVX state into extended region of XSAVE area;
FI;
IF RFBM[1] = 1 or RFBM[2] = 1
    THEN store MXCSR and MXCSR_MASK into legacy region of XSAVE area;
FI;
XSTATE_BV field in XSAVE header ← (OLD_BV AND ~RFBM) OR (XINUSE AND RFBM);</pre>
<h2>Flags Affected</h2>
<p>None.</p>
<h2>Intel C/C++ Compiler Intrinsic Equivalent</h2>
<p>XSAVE:</p>
<p>void _xsave( void * , unsigned __int64);</p>
<p>XSAVE:</p>
<p>void _xsave64( void * , unsigned __int64);</p>
<h2>Protected Mode Exceptions</h2>
<table class="exception-table">
<tr>
<td>#GP(0)</td>
<td>
<p>If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.</p>
<p>If a memory operand is not aligned on a 64-byte boundary, regardless of segment.</p></td></tr>
<tr>
<td>#SS(0)</td>
<td>If a memory operand effective address is outside the SS segment limit.</td></tr>
<tr>
<td>#PF(fault-code)</td>
<td>If a page fault occurs.</td></tr>
<tr>
<td>#NM</td>
<td>If CR0.TS[bit 3] = 1.</td></tr>
<tr>
<td>#UD</td>
<td>
<p>If CPUID.01H:ECX.XSAVE[bit 26] = 0.</p>
<p>If CR4.OSXSAVE[bit 18] = 0.</p>
<p>If any of the LOCK, 66H, F3H or F2H prefixes is used.</p></td></tr>
<tr>
<td>#AC</td>
<td>If this exception is disabled a general protection exception (#GP) is signaled if the memory operand is not aligned on a 16-byte boundary, as described above. If the alignment check exception (#AC) is enabled (and the CPL is 3), signaling of #AC is not guaranteed and may vary with implementation, as follows. In all implementations where #AC is not signaled, a general protection exception is signaled in its place. In addition, the width of the alignment check may also vary with implementation. For instance, for a given implementation, an align-ment check exception might be signaled for a 2-byte misalignment, whereas a general protec-tion exception might be signaled for all other misalignments (4-, 8-, or 16-byte misalignments).</td></tr></table>
<h2>Real-Address Mode Exceptions</h2>
<table class="exception-table">
<tr>
<td>#GP</td>
<td>
<p>If a memory operand is not aligned on a 64-byte boundary, regardless of segment.</p>
<p>If any part of the operand lies outside the effective address space from 0 to FFFFH.</p></td></tr>
<tr>
<td>#NM</td>
<td>If CR0.TS[bit 3] = 1.</td></tr>
<tr>
<td>#UD</td>
<td>
<p>If CPUID.01H:ECX.XSAVE[bit 26] = 0.</p>
<p>If CR4.OSXSAVE[bit 18] = 0.</p>
<p>If any of the LOCK, 66H, F3H or F2H prefixes is used.</p></td></tr></table>
<h2>Virtual-8086 Mode Exceptions</h2>
<p>Same exceptions as in protected mode.</p>
<h2>Compatibility Mode Exceptions</h2>
<p>Same exceptions as in protected mode.</p>
<h2>64-Bit Mode Exceptions</h2>
<table class="exception-table">
<tr>
<td>#GP(0)</td>
<td>
<p>If the memory address is in a non-canonical form.</p>
<p>If a memory operand is not aligned on a 64-byte boundary, regardless of segment.</p></td></tr>
<tr>
<td>#SS(0)</td>
<td>If a memory address referencing the SS segment is in a non-canonical form.</td></tr>
<tr>
<td>#PF(fault-code)</td>
<td>If a page fault occurs.</td></tr>
<tr>
<td>#NM</td>
<td>If CR0.TS[bit 3] = 1.</td></tr>
<tr>
<td>#UD</td>
<td>
<p>If CPUID.01H:ECX.XSAVE[bit 26] = 0.</p>
<p>If CR4.OSXSAVE[bit 18] = 0.</p>
<p>If any of the LOCK, 66H, F3H or F2H prefixes is used.</p></td></tr>
<tr>
<td>#AC</td>
<td>If this exception is disabled a general protection exception (#GP) is signaled if the memory operand is not aligned on a 16-byte boundary, as described above. If the alignment check exception (#AC) is enabled (and the CPL is 3), signaling of #AC is not guaranteed and may vary with implementation, as follows. In all implementations where #AC is not signaled, a general protection exception is signaled in its place. In addition, the width of the alignment check may also vary with implementation. For instance, for a given implementation, an align-ment check exception might be signaled for a 2-byte misalignment, whereas a general protec-tion exception might be signaled for all other misalignments (4-, 8-, or 16-byte misalignments).</td></tr></table></body></html>